Debian Admin posted a guide about using bzip2 and bunzip2 under Debian

bzip2 and bunzip2 are file compression and decompression utilities. The bzip2 and bunzip2 utilities are newer than gzip and gunzip and are not as common yet, but they are rapidly gaining popularity. The bzip2 utility is capable of greater compression ratios than gzip. Therefore, a bzip2 file can be 10-20% smaller than a gzip version of the same file. Usually, files that have been compressed by bzip2 will have a .bz2 extension.